Lens/Cataract/Refractive Flashcards
• Assessing pre-cataract sx VA potential
PAM, PAP (potential acuity pinhole)—dilate and show brightly lit near card through pinhole; LI (laser inferometry)—projects 2 separate laser beams on the retina which interfere with each other. The pattern is decreased until patient cannot distinguish separate lines.
• Relative contraindications to laser refractive surgery
connective tissue disease (RA, Sjogren, SLE, GPA); corneal ectatic disorders or corneal dystrophies, diabetic retinopathy, dry eye, Fuchs, meds including amiodarone or isotretinoin, monocular patients, neurotrophic corneas, pregnant or breastfeeding, age less than 18, history of HSV or VZV ophthalmicus, TED, uncontrolled DM.
• Time out of lenses prior to refractive surgery
regular soft contacts 3-14 days. Toric soft contacts 2 weeks. RGP lenses 2-3 weeks plus 1 month per decade of wear.
• Conductive keratoplasty:
radiofrequency to heat peripheral cornea which causes central steepening. Only good for low orders of hyperopia and does not treat astigmatism.
• Post-lasik IOL calcs using contact lens over-refraction
average Ks+ power of contact lens + CL over-refraction – spherical equivalent of manifest refraction. Usually post-lasik patients have an overestimation of corneal power by topography which can lead to a hyperopic surprise
• Post refractive IOL calc using clinical history
Kestimated = Kpre+Rpre-Rpost
• Posterior chamber phakic IOL vault:
vault over crystalline lens to avoid contact with it. Ideal vault is 1.0 +/- 0.5 corneal thickness (250-750 microns. Less than 250 microns risks anterior subcapsular cataract formation.
• Christmas tree cataracts
myotonic dystrophy OR hypoparathyroidism can cause it. With myotonic dystrophy you often see low intelligence, ptosis, CPEO. Peripheral pigmentary retinopathy, cardiac conduction abnormalities
• Lens capsule thickness
12-21 microns anteriorly and 2-9 microns posteriorly.
